RXTE Image Gallery
See images of:
XTE Spacecraft and Team
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Artist's impression of XTE observing a source.
Artist credit: NASA
Diagram of the XTE spacecraft, with instruments labeled
Diagram of the Delta II rocket with XTE spacecraft payload
XTE during assembly at Goddard Space Flight Center
Fully assembled XTE at Kennedy Space Center
XTE on the Launch Pad
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Credit: NASA.
At Launch Complex 17, Pad A, on Cape Canaveral Air Station a Radio Frequency Interference (RFI) test of the Delta 230 expendable launch vehicle is under way. During the prelaunch test, the service tower at the pad is rolled back and all Radio Frequency (RF) sources that support final countdown -- such as range tracking and launch control -- are radiated toward the vehicle to insure that no interference to the signals exists. Delta 230 is a Delta II 7920-configuration vehicle built by McDonnell Douglas Aerospace. Encapsulated atop the vehicle is the X-ray Timing Explorer (XTE), which the Delta will loft into a low-Earth orbit to begin a two-year mission to gather data about X-ray emitting objects in the Milky Way galaxy and beyond.
Photo # KSC-95PC-1797
Credit: NASA.
The mobile service tower has been rolled back at Launch Complex 17,
Pad A, to prepare for launch of NASA's X-ray Timing Explorer (XTE)
spacecraft atop the Delta 230 expendable launch vehicle. Once lofted into
orbit, the XTE spacecraft will embark on an approximately two-year mission
to carry out an
in-depth study of X-ray sources in the universe. The Delta 230 is built by
McDonnell Douglas Aerospace and is a Delta II 7920-configuration vehicle.
It features a new advanced technology avionics system that offers improved
reliability at reduced cost. The XTE vehicle and launch services are being
provided by McDonnell Douglas under a Medium Expendable Launch Vehicle
contract with NASA.
Photo # KSC-95PC-1842
Photo # KSC-95PC-1841
Credit: NASA.
A Delta II launch vehicle carrying the X-ray Timing Explorer (XTE)
lights up the sky at 8:48 a.m. EST, December 30, 1995. Liftoff occurred from
Launch Complex 17, Pad A, on Cape Canaveral Air Station under the management
of a combined government/contractor launch team that includes NASA, the Air
Force and McDonnell Douglas. The XTE spacecraft is outfitted with three
scientific instruments that will study X-rays, including their origin and
emission mechanisms, and the physical conditions and evolution of X-ray
sources within the Milky Way galaxy and beyond. The XTE is one is a series
of Explorer missions planned by NASA; it will perform its observations from
a vantage point in low Earth orbit for a mission duration expected to
last two to five years. The Delta II 7920 expendable launch vehicle
carrying the XTE spacecraft into orbit is provided by McDonnell Douglas.
Delta 230, as this vehicle was designated, is the first in the Delta family
to fly outfitted with a new advanced avionics system.
XTE Target Objects
![blue ball](https://webarchive.library.unt.edu/eot2008/20080921132258im_/http://heasarc.gsfc.nasa.gov/Images/heasarc/icons/blueball.gif)
Credit: David Malin; taken with the UK Schmidt telescope. © Royal Edinburgh and Anglo-Australian Telescope Board.
Supernova 1987a shortly after its outburst (left) completely
outshines its neighboring stars in the Large Magellanic Cloud. In a
pre-outburst photograph, the progenitor star which exploded is seen (arrow).
A rapidly spinning neutron star may be embedded in the debris of the
explosion. It could be seen first in X-rays as the debris expands and thins
out. (North is up)
Credit: David Malin; taken with the 3.9-m Anglo-Australian telescope.
© Anglo-Australian Telescope Board.
The size of a white dwarf is comparable to the Earth, but its mass
is up to 500,000 times greater. A neutron star has about the same mass as
the white dwarf, but it is extremely compact, only about 1/600 the size of
the Earth.
Credit: C. Jones, C. Stern, & W. Forman.
© Smithsonian Institution Astrophysical Observatory.
The Orion Nebula (In Orion's sword), shown here in visible light,
is the site of star formation and many young stars, some with intense
coronal activity visible in medium-energy X-rays. (North is left)
Credit: David Malin; taken with the UK Schmidt telescope.
© Royal Edinburgh and Anglo-Australian Telescope Board.
This view of the nearby galaxy Centaurus A in visible light shows
its elliptical distribution of starlight and a broad, dark dust lane. It is
roughly 15 million light years distant and has an active nucleus which
exhibits jets of optical, radio, and X-ray emission (see the next image).
(North is up)
Credit: David Malin; taken with the 3.9-m Anglo-Australian telescope.
© Anglo-Australian Telescope Board.
The X-ray jet emanating from the center of Centaurus A illustrates
the active nature of the nucleus (bright spot; lower right). It extends
about ~20,000 light years from the nucleus. The colors represent X-ray
intensity. (North is up)
Credit: C. Jones, C. Stern, & W. Forman; taken with the
Einstein X-ray Observatory
(HEAO 2); adapted from Feigelson et al, Ap. J., 251, 31.
© Smithsonian Institution Astrophysical Observatory.
The X-ray jet emanating from the center of Centaurus A illustrates
the active nature of the nucleus (bright spot; lower right). It extends
about ~20,000 light years from the nucleus. The colors represent X-ray
intensity. (North is up)
Credit: C. Jones, C. Stern, & W. Forman; taken with the
Einstein X-ray Observatory
(HEAO 2); adapted from Feigelson et al, Ap. J., 251, 31.
© Smithsonian Institution Astrophysical Observatory.
Close-up view of an accreting neutron star or white dwarf. The accreting
gas can be guided to the magnetic pole of the compact object where it creates a
hot spot that rotates into and out of sight as the compact star rotates. The
radiation from the spot can depart only in certain direction because of the
in-falling matter and strong magnetic fields. The results is an X-ray
"pulsar". Sketch courtesy of H. Bradt, M. Halverson, and students.
XTE Timing Studies
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The sudden commencement of accretion of gas from a low-mass star onto a
companion compact objects leads to a huge outpouring of relatively soft
X-ray emission, i.e. an X-ray nova.
This X-ray light curve from the
Ginga satellite show such an event. The flux can exceed that of the
brightest persistent X-ray sources. The study of the early phases of these
events with XTE will probe the cause of the sudden accretion. Optical
identifications should lead to new candidate black holes.
Be stars are luminous stars that occasionally eject clouds of plasma.
A neutron star in wide orbit about the
Be star will sometimes encounter the plasma and accrete some of it. The
accretion leads to transient X-ray emission which can be used to diagnose the
geometry and variability of the plasma ejections.
As the accretion rate decreased after flare maximum,
EXOSAT observers found that the rate of
the spin change in source EXO 2030+375 decreased systematically. (The
luminosity is a measure of the accretion rate.) This is as expected if the
torque applied to the neutron star is due to the accreting matter. It is
possible that the matter actually started slowing the spin rate (spindown) at
the end of the observations.
Rapid aperiodic pulsing
(quasi-periodic oscillations; QPO) in low-mass X-ray binaries is
probably due to interactions between the circulating matter in the accretion
disk and the magnetosphere of the neutron star. These pulsations are
directly seen with the Ginga
satellite during a burst of the "Rapid Burster" source. The
mechanism that gives rise to QPO pulsations is not yet known. They may be
symptomatic of a heretofore undetected pulsar spinning almost 1000 times a
second.
The character (intensity and frequency) of the oscillations of QPO
sources appears to depend on where the
sources is located on a two-color plot, as we see here in
EXOSAT data for Cyg
X-2. At any instant, the X-ray spectrum can be represented as a
point on this plot. Cyg X-2 is called a 'Z' source because of the shape of
the plot. The position at a given time is probably a measure of the
accretion rate. Such systematic behavior leads to the hope that the QPO
phenomenon will prove to be a powerful probe of the conditions in the outer
magnetosphere.
X-ray bursts are due to the explosive thermonuclear burning of gas on the
surface of neutron stars.
This is the discovery event found with the
Astronomische Nederlandse
Satelliet (ANS) satellite. The evolving spectrum of these burst
indicates that they come from an object about the size of a neutron star.
Spectral Studies with XTE
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A diffuse background of
X-rays is known to emanate from the whole sky. The origin of this is not
known although it is clear that at least some of it comes from many distant
active galactic nuclei (AGNs) which are known to emit X-rays. The possible
power-law spectra from AGN (straight lines) is generally flatter than the
background (data points and bars). If the AGN spectrum continues with the
same power law to energies above ~100 keV, the AGN emission would exceed the
background! It thus becomes imperative to measure the spectra of AGN at
energies beyond ~30 keV.
Multifrequency Studies with XTE
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Credit: Adapted from Silber et al 1992, ApJ, 389, 704.
High Energy X-ray Timing Experiment (HEXTE)
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HEXTE Fields of View. Diagram courtesy of Hale Bradt. M. Halverson,
and students.
A depiction of a Phoswich. Adapted from a diagram provided by
Hale Bradt. M. Halverson, and students.
Proportional Counter Array (PCA)
PCA diagrams are courtesy of Hale Bradt. M. Halverson, and students.The All Sky Monitor (ASM)
ASM diagrams are courtesy of Hale Bradt. M. Halverson, and students.![blue ball](https://webarchive.library.unt.edu/eot2008/20080921132258im_/http://heasarc.gsfc.nasa.gov/Images/heasarc/icons/blueball.gif)
Diagram of one of the ASM shadow cameras.
The Principle of a Shadow Camera.
XTE information
UCSD's HEXTE picture gallery
Images from other missions
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